This question implies something else: what are all the URLs referenced/accessed by Congress? The page says something different, and I believe the headline is misleading:
> This page is a public record of any time someone visits GovTrack.us from within the United States Senate, House of Representatives, or the White House, and their associated office buildings.
Of all pages one can browse on the web from within Congress machines, how relevant is GovTrack.us overall in that data? It's like saying the ISP publishes only my browsing data that happens to hit on my ISP's own website itself. Did I misunderstand something?
A better strategy would be to determine which ISP serves Congress, and pay them for the data of IPs originating from Congress.